1. Field of the Invention
The present invention relates generally to integrated circuits and, more particularly, to programmable semiconductor structures and methods for efficiently fabrication the same.
2. Description of the Related Art
There are a significant number of integrated circuit applications that require some sort of electrically programmable memory for storing information. The information stored varies widely in size ranging from a few bits used to program simple identification data, to several megabits used to program computer operating code. To accommodate the increased demand for electrically programmable memory in modern integrated circuits, a number of well known memory technologies are commonly used. Some example memory technologies include programmable read only memories (PROMs), erasable programmable read-only memories (EPROMs), electrically erasable programmable read-only memories (EEPROMs), field programmable gate arrays (FPGAs), fuse devices, antifuse devices, etc.
By way of example, FIG. 1 shows a semiconductor chip 100 that incorporates programmable memory 102. The programmable memory 102 will generally include memory devices 102a that may be programmably coupled to various control circuits that are part of the core CMOS circuitry that lies in the semiconductor chip 100. Although the programmable memory 102 works well, semi-custom fabrication is generally needed to manufacture and integrate the memory devices in conjunction with the core CMOS circuitry. Consequently, this type of integration will tend to be costly. In addition, the turn around time to complete this type of integration will also be higher than semiconductor chips that do not have programmable devices integrated therein. Furthermore, the additional product costs are often times difficult to justify when only a relatively small amount of electrically programmable elements are needed for a particular integrated circuit application.
In view of the foregoing, there is a need for programmable devices that can be cost effectively fabricated and programmed along with other standard CMOS circuitry.